Imperishable Night is a vertically-scrolling shooter by ZUN which features a total of eight playable characters in pre-set pairs. The pairs work in tandem: one person fires when unfocused, while the other pops in and fires when focused, with a reduction in movement speed. The two attacks can be drastically different.

Pressing the shift key slows down the player's movement, makes the collision box visible and focuses the player's attack to make it more powerful by switching your character with her Phantom teammate. This function is essential for navigating through complex bullet patterns and defeating bosses more quickly.

There are 4 levels of difficulty: Easy, Normal, Hard, and Lunatic. Each difficulty level features differences in the number of bullets fired by each enemy, rate of fire, variations in the bullets' pattern of movement, and the number and type of enemy Spell Cards used.

In this system, the game starts at 11:00 pm, and 1:00 is added after each stage. If enough time orbs are collected in the stage, 0:30 is added for that stage instead. 0:30 is also added in the case the player decides to continue. If the time reaches 5:00 am before the end of the last stage, the player receives a Game Over.

Boss have multiple lives, represented by multiple health bars shown at the upper left of the screen. Bosses usually alternate between attacking normally and attacking with Spell Cards, switching once with each health bar. Colored sections on the health bar indicate the start of a Spell Card attack when the boss' health is depleted that far.

Each attack is accompanied by a timer. When time runs out, the boss will switch to their next attack pattern even if their health bar isn't empty. Waiting for a boss character's attack pattern to self-destruct may be enough to beat them, but mere survival won't earn the player any score bonuses. Some bosses that are invulnerable, hence you will be awarded a score bonus if you survive the countdown to zero.

When fighting a boss, a position marker shows up on the bottom margin of the screen, indicating where the boss is on the horizontal axis. Since your target can be completely obscured by bullets or darkness at times, use this marker to help you aim your shots. The marker will dim when the boss is being hit, and will flash red when her health bar gets sufficiently depleted.